Early Detection and Monitoring of Anastomotic Leaks via Naked Eye‐Readable, Non‐Electronic Macromolecular Network Sensors

Abstract Anastomotic leakage (AL) is the leaking of non‐sterile gastrointestinal contents into a patient's abdominal cavity. AL is one of the most dreaded complications following gastrointestinal surgery, with mortality rates reaching up to 27%. The current diagnostic methods for anastomotic leaks are limited in sensitivity and specificity. Since the timing of detection directly impacts patient outcomes, developing new, fast, and simple methods for early leak detection is crucial. Here, a naked eye‐readable, electronic‐free macromolecular network drain fluid sensor is introduced for continuous monitoring and early detection of AL at the patient's bedside. The sensor array comprises three different macromolecular network sensing elements, each tailored for selectivity toward the three major digestive enzymes found in the drainage fluid during a developing AL. Upon digestion of the macromolecular network structure by the respective digestive enzymes, the sensor produces an optical shift discernible to the naked eye. The diagnostic efficacy and clinical applicability of these sensors are demonstrated using clinical samples from 32 patients, yielding a Receiver Operating Characteristic Area Under the Curve (ROC AUC) of 1.0. This work has the potential to significantly contribute to improved patient outcomes through continuous monitoring and early, low‐cost, and reliable AL detection.

Figure S3: IR-spectra of gelatin, Gel-MA and its corresponding hydrogel.The spectrum of gelatin is similar to literature with the major peaks corresponding to the various amide bonds found in this biomolecule. 56While in the spectra of Gel-MA and the Gel-MA Gel, the methacrylate C=C bands are overlapped by the characteristic amide bond bands, the spectra are in accordance with literature. 57,58igure S4: IR spectra of Acrylamide, Starch and the Starch-MA hydrogel.The acrylamide spectra is in accordance with literatures.The two bands from 3200-3400 cm -1 correspond to the primary amine found in acrylamide.While the bands around 1650 cm -1 correspond to the amide C=O stretch vibration and the band around 1600 cm -1 corresponds to the NH2δ vibration. 57,59The spectrum of starch is good accordance with literature.The strong bands around 1000 cm -1 correspond to the various C-O and C-C stretch modes while the broad band from 3000-3600 cm -1 stems potentially from adsorbed water as well as the O-H stretch vibration of the alcohol groups found in starch.The band around 2900 cm -1 likely corresponds to the C-H stretch modes. 57,60The Starch-MA hydrogel spectrum shows a good superposition of the two materials.S5: IR spectra of coconut oil, ethylcellulose and the resulting oleogel.The coconut oil displays two strong bands around 2900 cm -1 corresponding to the C-H stretch vibrations of the alkane chains and another strong band around 1750 cm -1 corresponding to the C=O stretch mode of the ester bonds found in the tryglyceride. 57While the bands found in the ethylcellulose spectrum are weak, is shows similarity to the starch spectrum.The bands around 1000 cm -1 correspond to the various C-O and C-C stretch modes and the band around 2950 cm -1 stemms from the C-H stretch modes. 57The spectrum of the oleogel has more similarity to the spectrum of coconut oil and the gel only contains 5 wt% ethylcellulose.However, the oleogel spectrum still shows a band broadening around 1000 cm -1 stemming from the ethylcelulose.Table S1: Enzyme activity of patient samples obtained from the University Hospital Zurich.From each patient the amylase and lipase activity was determined and it was noted whether or not a leak occurred.Patient #1 underwent total pancreaticoduodenectomy, the removal of the pancreas, during which several complications occurred, and a drain was placed directly into the GI tract of said patient.Therefore, the case does not classify as a leak.The heightened amylase and lipase levels are explained by the fact that through this procedure the patient is reliant on an external source of enzymes since his body can no longer produce them.The missing trypsin sensor response is explained by the fact, that the sensor used detects trypsin which the patient cannot produce themselves anymore and did not get supplemented with at the time.

Figure S1 :
Figure S1: Reaction scheme of the methacrylation of gelatin.Using methacrylic anhydride, amine and guanidine containing side chains of amino acids are methacrylated, resulting in a photocrosslinkable gelatin.

Figure S2 :
Figure S2: Reaction scheme of the methacrylation of starch.Using methacrylic anhydride, alcohol groups on starch are methacrylated, resulting in a photocrosslinkable starch.

Figure S7 :
Figure S7: Thin film fabrication and macromolecular network sensing elements manufacturing of Starch-MA (a), Oleogel (b) and Gel-MA (c).A biopsy punch was employed to excise sensing elements.

Figure S8 :
Figure S8: Swelling behavior of 25% acrylic acid hydrogels after immersion in different buffer solutions.Due to bigger distances between the gold particles a color change is visible.

Figure S9 :
Figure S9: Additional temperature data of Gel-MA and Starch-MA macromolecular sensing elements.

Figure S10 :
Figure S10: pH dependence of Gel-MA and Starch-MA macromolecular sensing elements at 30°C.

Table S2 :
Enzyme activity of pancreatin used for leak simulation experiments as determined by clinical chemistry.